My kid will be starting at UCI in the fall. I keep reading how everyone needs a car. How viable are biking, public transit, and Ubering to get around? My kid doesn’t need to be going to LA or wherever every weekend.
Public bus is available but pretty inconvenient. UCI has a shuttle service around the campus and to a couple of awesome places outside the campus, namely The District which has everything, and the mall where H-Mart is in which has everything Asian in it.
“mall where H-Mart is in which has everything Asian in it.” +1 for UCI’s decision matrix. 
My son does not have a car (although he is asking for one), He has plenty of friends who do not have cars. The shuttle does go to the Irvine Spectrum, The District, and Diamond Jamboree. I believe there is also a shuttle that goes to the UCI Medical Center which is conveniently located next to The Block at Orange. Many kids get by using bikes, Uber or hitching rides with friends who have cars. If your kid is interested in going to LA, he can take the OC Metrolink which will take him into LA in about an hour.
Also, the UTC (University Town Center) is right across the street from campus and includes a Target, Trader Joes, and a slew of restaurants and fast food places.
https://www.shopirvinecompany.com/centers/irvine/university-center
I think with Uber, you can probably get by without a car. The shuttles going to the locations that are far off campus aren’t that convenient and they’re kinda slow, but if you have a group of friends that you go out with, you can take turns paying for the Uber so hopefully it won’t be that bad.
S is a freshman @ UCI. He does not have a car, but does have an off campus job. Bikes to work. Uber or shuttle to Amtrak to come home or visit San Diego. Shared ride to volleyball tournaments. He seems too busy with on campus activities (studying, class, dorm activities, clubs, on campus events, …) to need the hassle or cost of a car. YMMV, just one data point.
yeah, we visited UCI during their open house a couple of weeks ago. dont think i will stress about him needing a car anymore.
You’ll find that you’ll eventually need to find a friend who has a car. A car is not necessary but opens so much to you when you wanna go out